Double self-aligned via patterning

ABSTRACT

A method including forming a penta-layer hardmask above a substrate, the penta-layer hardmask comprising a first hardmask layer above a second hardmask layer; forming a trench pattern in the first hardmask layer; transferring a first via bar pattern from a first photo-resist layer above the penta-layer hardmask into the second hardmask layer resulting in a first via pattern, the first via pattern in the second hardmask layer overlapping the trench pattern and being self-aligned on two sides by the trench pattern in the first hardmask layer; and transferring the first via pattern from the second hardmask layer into the substrate resulting in a self-aligned via opening, the self-aligned via opening being self-aligned on all sides by the first via pattern in the second hardmask layer.

BACKGROUND

1. Field of the Invention

The present invention generally relates to semiconductor devicemanufacturing, and more particularly to an improved technique foretching self-aligned via holes and wiring paths into a dielectric layerwherein the via holes self-align to the wiring paths.

2. Background of Invention

Semiconductor device manufacturing generally includes various stepsincluding a patterning process. For example, the manufacturing of asemiconductor chip may start with, for example, CAD (computer aideddesign) generated device patterns and may continue with the effort toreplicate these device patterns in a substrate in which semiconductordevices can be formed. The replication process may involve the use of aphotolithography process in which a layer of photo-resist material maybe first applied on top of a substrate, and then be selectively exposedaccording to a pre-determined device pattern. Portions of thephoto-resist that are exposed to light or other ionizing radiation(e.g., ultraviolet, electron beams, X-rays, etc.) may experience somechanges in their solubility to a certain solution. Next, thephoto-resist may be developed in a developer solution, thereby removingthe non-irradiated (in a negative resist) or irradiated (in a positiveresist) portions of the resist layer, to create a photo-resist pattern.The photo-resist pattern may subsequently be copied or transferred tothe substrate underneath the photo-resist pattern.

SUMMARY

According to one exemplary embodiment of the present invention, a methodis provided. The method may include forming a penta-layer hardmask abovea substrate, the penta-layer hardmask comprising a first hardmask layerabove a second hardmask layer; forming a trench pattern in the firsthardmask layer; transferring a first via bar pattern from a firstphoto-resist layer above the penta-layer hardmask into the secondhardmask layer resulting in a first via pattern, the first via patternin the second hardmask layer overlapping the trench pattern and beingself-aligned on two sides by the trench pattern in the first hardmasklayer; and transferring the first via pattern from the second hardmasklayer into the substrate resulting in a self-aligned via opening, theself-aligned via opening being self-aligned on all sides by the firstvia pattern in the second hardmask layer.

According to another exemplary embodiment of the present invention, amethod is provided. The method may include forming a penta-layerhardmask above a substrate, the penta-layer hardmask comprising a firsthardmask layer above a second hardmask layer; forming a trench patternin the first hardmask layer; and forming a self-aligned via opening inthe substrate below the trench pattern, the self-aligned via openingbeing self-aligned on all sides by a self-aligned via pattern in thesecond hardmask layer.

According to another exemplary embodiment of the present invention, amethod is provided. The method may include forming a penta-layerhardmask above a substrate, the penta-layer hardmask comprising a firsthardmask layer above a second hardmask layer; forming a trench patternin the first hardmask layer; transferring a first via bar pattern from afirst photo-resist layer above the penta-layer hardmask into the secondhardmask layer resulting in a first via pattern, the first via patternin the second hardmask layer overlapping the trench pattern and beingself-aligned on two sides by the trench pattern in the first hardmasklayer; transferring a second via bar pattern from a second photo-resistlayer above the penta-layer hardmask into the second hardmask layerresulting in a second via pattern, the second via pattern in the secondhardmask layer overlapping the trench pattern and being self-aligned ontwo sides by the trench pattern in the first hardmask layer; andtransferring the first via pattern and the second via pattern from thesecond hardmask layer into the substrate resulting in a self-aligned viaopening, the self-aligned via opening being self-aligned on all sides bythe first via pattern in the second hardmask layer.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The following detailed description, given by way of example and notintended to limit the invention solely thereto, will best be appreciatedin conjunction with the accompanying drawings, in which:

FIG. 1 is a cross-sectional view of a structure at an intermediate stepof fabrication according to an exemplary embodiment.

FIG. 2 is a top view of the structure and illustrates forming a trenchpattern in a first hardmask layer according to an exemplary embodiment.

FIG. 2A is a cross section view of FIG. 2, taken along section line A-A.

FIG. 2B is a cross section view of FIG. 2, taken along section line B-B.

FIG. 3 is a top view of the structure and illustrates forming a firstvia bar pattern in a first ARC layer, a first planarization layer, and asecond pattering layer according to an exemplary embodiment.

FIG. 3A is a cross section view of FIG. 3, taken along section line A-A.

FIG. 3B is a cross section view of FIG. 3, taken along section line B-B.

FIG. 4 is a top view of the structure and illustrates forming the firstvia bar pattern in a second hardmask layer according to an exemplaryembodiment.

FIG. 4A is a cross section view of FIG. 4, taken along section line A-A.

FIG. 4B is a cross section view of FIG. 4, taken along section line B-B.

FIG. 5 is a top view of the structure and illustrates forming a secondvia bar pattern in a second ARC layer, a second planarization layer, andthe second pattering layer according to an exemplary embodiment.

FIG. 5A is a cross section view of FIG. 5, taken along section line A-A.

FIG. 6 is a top view of the structure and illustrates forming the secondvia bar pattern in the second hardmask layer according to an exemplaryembodiment.

FIG. 6A is a cross section view of FIG. 6, taken along section line A-A.

FIG. 7 is a top view of the structure and illustrates transferring adual self-aligned via pattern from the second hardmask layer to asubstrate according to an exemplary embodiment.

FIG. 7A is a cross section view of FIG. 7, taken along section line A-A.

FIG. 7B is a cross section view of FIG. 7, taken along section line B-B.

FIG. 8 is a top view of the structure and illustrates transferring thetrench pattern from the first hardmask layer to the second hardmasklayer.

FIG. 8A is a cross section view of FIG. 8, taken along section line A-A.

FIG. 8B is a cross section view of FIG. 8, taken along section line B-B.

FIG. 9 is a top view of the structure and illustrates transferring thedamascene pattern from the second hardmask layer to the substrateaccording to an exemplary embodiment.

FIG. 9A is a cross section view of FIG. 9, taken along section line A-A.

FIG. 9B is a cross section view of FIG. 9, taken along section line B-B.

FIG. 10 is a top view of the structure and illustrates forming the finalstructure according to an exemplary embodiment.

FIG. 10A is a cross section view of FIG. 10, taken along section lineA-A.

FIG. 10B is a cross section view of FIG. 10, taken along section lineB-B.

The drawings are not necessarily to scale. The drawings are merelyschematic representations, not intended to portray specific parametersof the invention. The drawings are intended to depict only typicalembodiments of the invention. In the drawings, like numbering representslike elements.

DETAILED DESCRIPTION

Detailed embodiments of the claimed structures and methods are disclosedherein; however, it can be understood that the disclosed embodiments aremerely illustrative of the claimed structures and methods that may beembodied in various forms. This invention may, however, be embodied inmany different forms and should not be construed as limited to theexemplary embodiments set forth herein. Rather, these exemplaryembodiments are provided so that this disclosure will be thorough andcomplete and will fully convey the scope of this invention to thoseskilled in the art. In the description, details of well-known featuresand techniques may be omitted to avoid unnecessarily obscuring thepresented embodiments.

References in the specification to “one embodiment”, “an embodiment”,“an example embodiment”, etc., indicate that the embodiment describedmay include a particular feature, structure, or characteristic, butevery embodiment may not necessarily include the particular feature,structure, or characteristic. Moreover, such phrases are not necessarilyreferring to the same embodiment. Further, when a particular feature,structure, or characteristic is described in connection with anembodiment, it is submitted that it is within the knowledge of oneskilled in the art to affect such feature, structure, or characteristicin connection with other embodiments whether or not explicitlydescribed.

For purposes of the description hereinafter, the terms “upper”, “lower”,“right”, “left”, “vertical”, “horizontal”, “top”, “bottom”, andderivatives thereof shall relate to the disclosed structures andmethods, as oriented in the drawing figures. The terms “overlying”,“atop”, “on top”, “positioned on” or “positioned atop” mean that a firstelement, such as a first structure, is present on a second element, suchas a second structure, wherein intervening elements, such as aninterface structure may be present between the first element and thesecond element. The term “direct contact” means that a first element,such as a first structure, and a second element, such as a secondstructure, are connected without any intermediary conducting, insulatingor semiconductor layers at the interface of the two elements.

In the interest of not obscuring the presentation of embodiments of thepresent invention, in the following detailed description, someprocessing steps or operations that are known in the art may have beencombined together for presentation and for illustration purposes and insome instances may have not been described in detail. In otherinstances, some processing steps or operations that are known in the artmay not be described at all. It should be understood that the followingdescription is rather focused on the distinctive features or elements ofvarious embodiments of the present invention.

Engineers are continuously facing the challenge of how to meet themarket demand for ever increasing device density. Some techniques usedto increase device density may require sub-lithographic (i.e., of a sizesmaller than can be produced using conventional lithographic processes)mask images, and which may require increased accuracy to preventunwanted misalignment. As such, it would also be desirable to have aprocess where vias self-align themselves to their respective metal linesduring their creation.

Embodiments of the present invention describe an improved technique foretching via holes and wiring paths into a dielectric layer wherein thevia holes self-align to the wiring paths.

A preferred embodiment includes using a trench-first metal hard mask(TFMHM) sequence wherein a first sub-lithographic trench pattern(corresponding to a wiring path) is etched into a first hardmask layerusing, for example, a sidewall image transfer technique. This isfollowed by etching a via opening into a second hardmask layer below thefirst hardmask layer. The via opening in the second hardmask layer maybe formed by patterning a second sub-lithographic trench pattern,otherwise referred to as a via bar pattern, across and perpendicular tothe first trench. After etching, the via opening in the second hardmasklayer may be formed only where the first trench and the via bar patternintersect. I n the present embodiment, the via opening may be consideredself-aligned in a via bar direction by the first trench pattern in thefirst hardmask layer. Lastly, the via pattern may be transferred fromthe second hardmask into an underlying substrate. The final via openingin the substrate may also be self-aligned in a first trench direction bythe second hardmask layer. It should be noted that the via bar directioncan generally refer to a direction along the length of any one of thevia bar features, and the first trench direction can generally refer toa direction along the length of any one of the first trench features.

FIG. 1 is a demonstrative illustration of a structure during anintermediate step of a method of double patterning a self-aligned via(SAV) according to one embodiment. More specifically, the method canstart with providing a penta-layer hardmask 104 above a substrate 102 inwhich the SAV is to be formed. The penta-layer hardmask 104 can furtherinclude, for example, a first patterning layer 106, a first hardmasklayer 108, a second patterning layer 110, a second hardmask layer 112,and a third patterning layer 114 all of which can be formed on top ofone another and in sequence.

In one embodiment, the substrate 102 at the bottom of the penta-layerhardmask 104 can be any dielectric materials suitable for BEOL or MOLinterconnect structures. In an alternative embodiment the substrate 102can be any gate materials suitable for FEOL structures. In otherembodiments, the substrate 102 can be a semiconductor material or adielectric material on top of a semiconductor material. The first,second, and third patterning layers 106, 110, 114 can include siliconoxide and can be formed, for example, from a tetraethyl orthosilicate(TEOS) precursor to have a thickness, in some embodiments, ranging fromabout 10 nanometers (nm) to about 100 nm. The first and second hardmasklayers 108, 112 can include titanium-nitride (TiN), titaniumanti-reflective coating (TiARC), hafnium anti-reflective coating(hfARC), amorphous carbon (a-C), carbon (a-Si), or NBlock and can have athickness, in some embodiments, ranging from about 10 nm to about 70 nm.The first and second hardmask layers 108, 112 can preferably, althoughnot necessarily, be formed to have the same or close to the samethickness to facilitate an etching process as described in more detailbelow.

FIGS. 2, 2A, and 2B are a demonstrative illustration of the structureduring an intermediate step of a method of double patterning aself-aligned via (SAV) according to one embodiment. More specifically,the method can start with forming a trench pattern in a penta-layerhardmask 104 above a substrate 102. FIG. 2 illustrates the structure 100from a top view. FIG. 2A is a cross section view of FIG. 2 taken alongsection line A-A. FIG. 2B is a cross section view of FIG. 2 taken alongsection line B-B. Therefore, FIG. 2A is a cross sectional viewperpendicular to the length of the trenches of the trench pattern 116,and FIG. 2B is a cross sectional view parallel to the length of thetrenches of the trench pattern 116. The trench pattern 116 may betransferred into the first hardmask layer 108 using, for example, knownsidewall image transfer techniques. Any other method known in the artcan be used to form the trench pattern 116 in the first hardmask layer108. It should be noted that formation of the trench pattern 116 in thefirst hardmask layer 108, also includes etching through the firstpatterning layer 106 as illustrated in the figures.

In one embodiment, the trench pattern 116 can have sub-lithographicdimensions. A sidewall image transfer technique can be used to achievesub-lithographic features and feature spacing, as is known in the art.The term “sub-lithographic” may refer to a dimension or size less thancurrent dimensions achievable by photolithographic processes, and theterm “lithographic” may refer to a dimension or size equal to or greaterthan current dimensions achievable by photolithographic processes. Thesub-lithographic and lithographic dimensions may be determined by aperson of ordinary skill in the art at the time the application isfiled. In another embodiment, double patterning techniques well known inthe art may be use to form the trench pattern 116 in the first hardmasklayer 106.

The trench pattern 116 may include one or more trench features, asillustrated in the figures. The sub-lithographic dimension of any onetrench feature may generally refer to the width and not necessarily thelength, the width generally being the smaller dimension of the two.Furthermore, any one trench feature of the trench pattern 116 may haveany length suitable for its intended application; however the length isnot critical to the present invention.

FIGS. 3, 3A, and 3B are a demonstrative illustration of the structureduring an intermediate step of a method of double patterning aself-aligned via (SAV) according to one embodiment. More specifically,the method can include a first stage of a double patterning technique inwhich a first via bar pattern 124 can be transferred into a firstplanarization layer 118 and a first anti-reflective coating layer 120(hereinafter “ARC” layer). FIG. 3 illustrates the structure 100 from atop view. FIG. 3A is a cross section view of FIG. 3 taken along sectionline A-A. FIG. 3B is a cross section view of FIG. 3 taken along sectionline B-B.

The first via bar pattern 124 can include one or more via bar features,each of which is oriented above and in a perpendicular fashion relativeto any one of the trench features of the trench pattern 116. First, asillustrated in FIGS. 3A and 3B, the first planarization layer 118, thefirst ARC layer 120, and a first photo-resist layer 122 all of which canbe formed on top of one another and in sequence.

The first planarization layer 118 can be an organic planarization layer(OPL) or a layer of material that is capable of being planarized byknown chemical mechanical polishing techniques. In one embodiment, forexample, the first planarization layer 118 can be an amorphous carbonlayer able to withstand the high process temperatures of subsequentprocessing steps. The first planarization layer 118 can preferably havea thickness ranging from about 10 nm to about 300 nm. The first ARClayer 120 can include silicon (Si) and in some embodiments can bereferred to as a SiARC layer or a bottom anti-reflective coating layer(BARC). The first ARC layer 120 can have a thickness ranging from about10 nm to about 100 nm in some embodiments.

During this step, a first photo-resist layer 122 can be formed on top ofthe first ARC layer 120. The first photo-resist layer 122 can includeany suitable photo-resist material. The particular photo-resist materialchosen can partly depend upon the desired pattern to be formed and theexposure method used. In one embodiment, the first photo-resist layer122 can include a single exposure resist suitable for, for example,argon fluoride (ArF); a double exposure resist suitable for, forexample, a thermal cure system; or an extreme ultraviolet (EUV) resistsuitable for, for example, an optical process. In one embodiment, thefirst photo-resist layer 122 can be formed with a thickness ranging fromabout 30 nm to about 150 nm. The first photo-resist layer 122 can thenbe lithographically exposed and developed to create the first via barpattern 124. The first via bar pattern 124 can be formed by applying anyappropriate photo-exposure method suitable to the type of photo-resistlayer being used, as is well known in the art.

More specifically, the first via bar pattern 124 can be transferred fromthe first photo-resist layer 122 into underlying layers, for example,the first ARC layer 120 and the first planarization layer 118.Transferring of the first via bar pattern 124 in the present step can beperformed by etching the first ARC layer 120 and the first planarizationlayer 118 selective to the second hardmask layer 112. A directionaletching technique such as a reactive-ion-etching technique can be usedto etch the first ARC layer 120 and the first planarization layer 118.In one embodiment, the first ARC layer 120 can be etched with areactive-ion-etching technique using a fluorocarbon based etchant, andthe first planarization layer 118 can be etched with areactive-ion-etching technique using an oxygen based etchant. In thepresent step, the first photoresist layer 122 can function as a maskduring etching of the first ARC layer 120, and can be removed duringetching of the first planarization layer 118. In this instance, thefirst ARC layer 120 can function as a mask during etching of the firstplanarization layer 118. Further, the second patterning layer 110 canfunction as an etch-stop layer during etching of the first planarizationlayer 118.

After transferring the first via bar pattern 124 into the firstplanarization layer 118 and the first ARC layer 120, the first via barpattern 124 can be transferred into the second patterning layer 110exposed by the trench pattern 116. Transferring the first via barpattern 124 in the present step can be performed by etching the secondpatterning layer 110 selective to the second hardmask layer 112. Adirectional etching technique such as a reactive-ion-etching techniquecan be used to etch the second patterning layer 110. In one embodiment,the second patterning layer 110 can be etched with areactive-ion-etching technique using a fluorocarbon based etchant. Inthe present step, the first planarization layer 118 can function as amask and the first ARC layer 120 can be thinned or removed duringetching of the second patterning layer 110. Further, the second hardmasklayer 112 can function as an etch-stop layer during the etching of thesecond patterning layer 110.

FIGS. 4, 4A, and 4B are a demonstrative illustration of the structureduring an intermediate step of a method of double patterning aself-aligned via (SAV) according to one embodiment. More specifically,the method can include continuation of the first stage of the doublepatterning technique in which the first via bar pattern 124 can betransferred from the first planarization layer 118 into the secondhardmask layer 112 of the a penta-layer hardmask 104. FIG. 4 illustratesthe structure 100 from a top view. FIG. 4A is a cross section view ofFIG. 4 taken along section line A-A. FIG. 4B is a cross section view ofFIG. 4 taken along section line B-B.

Transferring of the first via bar pattern 124 (FIG. 3) in the presentstep can be performed by etching the second hardmask layer 112 selectiveto the third patterning layer 114. A directional etching technique suchas a reactive-ion-etching technique can be used to etch the secondhardmask layer 112. In one embodiment, the second hardmask layer 112 canbe etched with a reactive-ion-etching technique using a fluorocarbon gasbased breakthrough step first, then followed by chlorine based etchant.In the present step, any remaining portion of the first ARC layer 120will be removed during the breakthrough step, and the firstplanarization layer 118 can function as the primary mask for etching ofthe second hardmask layer 112.

Thereafter, the first planarization layer 118 (FIG. 3) can be removed orlifted off The first planarization layer 118 (FIG. 3) can be stripped orremoved with either a wet clean technique, for example SP clean, or witha plasma etching technique using an oxygen based plasma. It should benoted that only a portion of the via bar pattern 124 (FIG. 3) can betransferred into the second hardmask layer 112. The portion of the viabar pattern 124 (FIG. 3) transferred into the second hardmask layer 112can be referred to as a self-aligned via (SAV) pattern, where only theoverlapping area between the via bar pattern 124 (FIG. 3) and the trenchpattern 116 (FIG. 2) will be transferred, and a portion of the via barpattern 124 (FIG. 3) outside the trench will not be transferred.

FIGS. S and SA are a demonstrative illustration of the structure duringan intermediate step of a method of double patterning a self-aligned via(SAV) according to one embodiment. More specifically, the method caninclude a second stage of the double patterning technique in which asecond via bar pattern 132 can be transferred into a secondplanarization layer 126 and a second anti-reflective coating layer 128(hereinafter “ARC” layer). FIG. S illustrates the structure 100 from atop view. FIG. SA is a cross section view of FIG. S taken along sectionline A-A. It should be noted that the second sage of the doublepatterning technique described below is substantially similar to thefirst stage described above; however, the second stage can be applied toan alternate location in accordance with known double patterningtechniques.

First, as illustrated in the figures, the second planarization layer126, the second ARC layer 128, and a second photo-resist layer 130 canbe formed on top of one another and in sequence above the structure 100.The second via bar pattern 132 is substantially similar to the first viabar pattern 124 described above. Also, the second planarization layer126 and the second ARC layer 128 are substantially similar to the firstplanarization layer 118 and the first ARC layer 120 described above.

During this step, the second photo-resist layer 130 can be formed on topof the second ARC layer 128. The second photo-resist layer 130 issubstantially similar to the first photo-resist 122 described above. Thesecond photo-resist layer 130 can then be lithographically exposed anddeveloped to create the second via bar pattern 132. Like above, thesecond via bar pattern 132 can be formed by applying any appropriatephoto-exposure method suitable to the type of photo-resist layer beingused, as is well known in the art. Also like above, the second via barpattern 132 can be transferred from the first photo-resist layer 130into underlying layers, for example, the second ARC layer 128 and thesecond planarization layer 126. Next, the second via bar pattern 132 canbe transferred into the second patterning layer 110, like above.

FIGS. 6 and 6A are a demonstrative illustration of the structure duringan intermediate step of a method of double patterning a self-aligned via(SAV) according to one embodiment. More specifically, the method caninclude continuation of the second stage of the double patterningtechnique in which the second via bar pattern 132 can be transferredfrom the second planarization layer 126 into the second hardmask layer112 of the a penta-layer hardmask 104. FIG. 6 illustrates the structure100 from a top view. FIG. 6A is a cross section view of FIG. 6 takenalong section line A-A. The second via bar pattern 132 can betransferred into the second hardmask layer 112, and the second ARC layer128 and the second planarization layer 126 can be removed as describedabove with reference to FIG. 4. Again, it should be noted that only aportion of the via bar pattern 132 (FIG. 5) can be transferred into thesecond hardmask layer 112. The portion of the via bar pattern 132 (FIG.5) transferred into the second hardmask layer 112 can be referred to asthe self-aligned via (SAV) pattern, as described above

FIGS. 7, 7A, and 7B are a demonstrative illustration of the structureduring an intermediate step of a method of double patterning aself-aligned via (SAV) according to one embodiment. More specifically,the method can include etching the SAV pattern into the underlyingsubstrate, the SAV pattern being defined by the second hardmask layer112. Again, the SAV pattern can refer to the portions of the first andsecond via bar patterns 124, 132 transferred into the second hardmasklayer 112, as described above with reference to FIGS. 3-6. FIG. 7illustrates the structure 100 from a top view. FIG. 7A is a crosssection view of FIG. 7 taken along section line A-A. FIG. 7B is a crosssection view of FIG. 7 taken along section line B-B.

Transferring the SAV pattern in the present step can be performed byetching the third patterning layer 114 and the substrate 102 to adesired depth. The desired depth can depend on the ultimate function ofthe structure 100. A directional etching technique such as areactive-ion-etching technique can be used to etch the third patterninglayer 114 and the substrate 102. In one embodiment, the third patterninglayer 114 and the substrate 102 can be etched with areactive-ion-etching technique using a fluorocarbon based etchant. Inthe present step, the second hardmask layer 112 can function as a mask,and can have a high etch-selectivity relative to the third patterninglayer 114 and the substrate 102. Furthermore, the first patterning layer106 (FIG. 6) can be simultaneously removed from above the first hardmasklayer 10S during etching of the SAV pattern.

FIGS. S, SA, and SB are a demonstrative illustration of the structureduring an intermediate step of a method of double patterning aself-aligned via (SAV) according to one embodiment. More specifically,the method can include transferring the trench pattern 116 from thefirst hardmask layer 10S to the second hardmask layer 112. FIG. Sillustrates the structure 100 from a top view. FIG. SA is a crosssection view of FIG. S taken along section line A-A. FIG. SB is a crosssection view of FIG. S taken along section line B-B.

Transferring the trench pattern 116 of the first hardmask layer 10S inthe present step can be performed by etching the second hardmask layer112 selective to the second and third patterning layers 110, 114. Adirectional etching technique such as a reactive-ion-etching techniquecan be used to etch the second hardmask layer 112. In one embodiment,the second hardmask layer 112 can be etched with a reactive-ion-etchingtechnique using a fluorocarbon plasma breakthrough step, followed by achlorine based etchant. In the present step, the second patterning layer110 can function as a mask, and the third patterning layer 114 canfunction as an etch-stop layer during the etching of the second hardmask112. Furthermore, the first hardmask layer 10S (FIG. 7) can besimultaneously removed during transferring the trench pattern 116 intothe second hardmask layer 112.

FIGS. 9, 9A, and 9B are a demonstrative illustration of the structureduring an intermediate step of a method of double patterning aself-aligned via (SAV) according to one embodiment. More specifically,the method can include etching the trench pattern 116 now defined by thesecond hardmask layer 112 into the underlying substrate 102. FIG. 9illustrates the structure 100 from a top view. FIG. 9A is a crosssection view of FIG. 9 taken along section line A-A. FIG. 9B is a crosssection view of FIG. 9 taken along section line B-B.

Transferring the trench pattern 116 in the present step can be performedby etching the third patterning layer 114 and the substrate 102 to adesired depth. The desired depth can depend on the ultimate function ofthe structure 100. A directional etching technique such as areactive-ion-etching technique can be used to etch the third patterninglayer 114 and the substrate 102. In one embodiment, the third patterninglayer 114 and the substrate 102 can be etched with areactive-ion-etching technique using a fluorocarbon based etchant. Inthe present step, the second hardmask layer 112 can function as a mask,and can have a high etch-selectivity relative to the third patterninglayer 114 and the substrate 102. Furthermore, the second patterninglayer 110 (FIG. 8) can be simultaneously removed from above the secondhardmask layer 112 during etching of the via pattern.

FIGS. 10, IOA, and IOB are a demonstrative illustration of a final of amethod of double patterning a self-aligned via (SAV) according to oneembodiment. More specifically, the final structure can include aninterconnect structure 134 formed by filling the SAV pattern and thetrench pattern 116 with a conductive interconnect material. FIG. 10illustrates the structure 100 from a top view. FIG. IOA is a crosssection view of FIG. 10 taken along section line A-A. FIG. IOB is across section view of FIG. 10 taken along section line B-B. In oneembodiment, typical processing techniques known in the art can be usedto fill the SAV pattern and the trench pattern 116 with a conductiveinterconnect material to form the interconnect structure 134.

The above described double patterning a self-aligned via (SAV) techniquecan have distinct advantages over other comparable techniques. Theprocess window of the traditional patterning of self-aligned via barsmay restricted by limited control of critical dimensions, high aspectratios, and mask corner rounding issues uncorrectable by opticalproximity correction. Furthermore, typical double patterning techniquesrequire at least two hardmask layers, two ARC layers, and twoplanarization layers all stacked on top of one another. The additionalstack height yields poor uniformity in the resulting via.

The descriptions of the various embodiments of the present inventionhave been presented for purposes of illustration, but are not intendedto be exhaustive or limited to the embodiments disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of the describedembodiments. The terminology used herein was chosen to best explain theprinciples of the embodiment, the practical application or technicalimprovement over technologies found in the marketplace, or to enableothers of ordinary skill in the art to understand the embodimentsdisclosed herein.

What is claimed:
 1. A method comprising: forming a penta-layer hardmaskabove a substrate, the penta-layer hardmask comprising a first hardmasklayer above a second hardmask layer; forming a trench pattern in thefirst hardmask layer; transferring a first via bar pattern from a firstphoto-resist layer above the penta-layer hardmask into the secondhardmask layer resulting in a first via pattern, the first via patternin the second hardmask layer overlapping the trench pattern and beingself-aligned on two sides by the trench pattern in the first hardmasklayer; transferring a second via bar pattern from a second photo-resistlayer above the penta-layer hardmask into the second hardmask layerresulting in a second via pattern, the second via pattern in the secondhardmask layer overlapping the trench pattern and being self-aligned ontwo sides by the trench pattern in the first hardmask layer; andtransferring the first via pattern and the second via pattern from thesecond hardmask layer into the substrate resulting in a self-aligned viaopening, the self-aligned via opening being self-aligned on all sides bythe first via pattern in the second hardmask layer.
 2. The method ofclaim 1, wherein the first via pattern and the second via pattern aresimultaneously transferred from the second hardmask layer into thesubstrate.
 3. The method of claim 1, wherein forming the penta-layerhardmask above the substrate comprises: depositing a third patterninglayer above the substrate; depositing the second hardmask layer abovethe first patterning layer; depositing a second patterning layer abovethe second hardmask layer; depositing the first hardmask layer above thesecond patterning layer; and depositing a first patterning layer abovethe first hardmask layer.
 4. The method of claim 1, wherein transferringthe first via bar pattern from the first photo-resist layer above thepenta-layer hardmask into the second hardmask layer resulting in thefirst via pattern comprises: depositing a first anti-reflective coating(ARC) layer above a first planarization layer above the penta-layerhardmask; forming the first via bar pattern in the first photo-resistlayer into the first ARC layer and the first planarization layer;transferring the first via bar pattern from the first photo-resist layerinto the first ARC layer and the first planarization layer; transferringthe first via bar pattern from the first ARC layer and the firstplanarization layer into the second hardmask; and removing the firstblock ARC layer and the first block planarization layer.
 5. The methodof claim 1, wherein transferring the second via bar pattern from thesecond photo-resist layer above the penta-layer hardmask into the secondhardmask layer resulting in the second via pattern comprises: depositinga second anti-reflective coating (ARC) layer above a secondplanarization layer above the penta-layer hardmask; forming the secondvia bar pattern in the second photo-resist material on top of the secondARC layer; transferring the second via bar pattern from the secondphoto-resist layer into the second ARC layer and the secondplanarization layer; transferring the second via bar pattern from thesecond ARC layer and the second planarization layer into the secondhardmask; and removing the second block ARC layer and the second blockplanarization layer.
 6. The method of claim 1, further comprising:transferring the trench pattern into the substrate.
 7. The method ofclaim 6, wherein transferring the trench pattern into the substratecomprises: transferring the trench pattern from the first hardmask layerinto the second hardmask layer; and transferring the trench pattern fromthe second hardmask layer into the substrate.